As anthracycline antibiotics there are hitherto known daunomycin (cf. U.S. Pat. No. 3,616,242) and adriamycin (cf. U.S. Pat. No. 3,590,028) obtained from culture solutions of Actinomyces. These compounds exhibit broad anti-tumor spectra against experimental tumors and have been widely used as cancer chemotherapy agents also for clinical purposes. However, daunomycin and adriamycin are not always satisfactory although they exhibit considerably potent anti-cancer activity. Various attempts have been made to produce analogous compounds by various means such as a fermentation method, a semisynthesis method, a method for conversion of microorganisms, etc. and some anthracycline antibiotics have additionally been proposed [for example, Published Examined Japanese Patent Application No. 34915/76 (aclacinomycins A and B), T. OKI et al., The Journal of Antibiotics, vol. 33, pages 1331 to 1340; F. Areamone, Topics in Antibiotic Chemistry, Vol. 2, pages 102 to 279, published by ELLIS HORWOOD LIMITED; Published Japanese Patent Application No. 56494/82 (4-demethoxy-11-deoxydaunomycin, etc.); Published Unexamined Japanese Patent Application No. 15299/81 (cf. rhodomycin series antibiotics) and the like]
As anthracycline antibiotics as anti-tumor agents, a variety of analogous compounds have been proposed as described above and have been widely used in part for clinical purpose and also provided in part for clinical tests.
However, none of them is satisfactory in either toxicity or anti-tumor activity. In addition, in anti-tumor agents, the results of in vitro and animal tests do not necessarily reflect anti-tumor activity of humans directly so that investigations are required from various aspects. For this reason, with respect to anthracycline antibiotics apparently evaluated as anti-tumor agents, it has been desired to propose compounds belonging to a new class.
As a result of extensive investigations with an attempt to propose more effective anthracycline antibiotics or novel compounds capable of being synthesis intermediates thereof, the present inventors have found that Streptomyces violaceus A 262 strain belonging to the rhodomycin-producing bacteria can produce novel anthracycline antibiotics and have accomplished the present invention.